The present invention relates to a semiconductor device and a method of manufacture thereof and more particularly to a technology effectively applied to a semiconductor device and a method of manufacture thereof, the device having a structure in which a semiconductor pellet is mounted on a pellet mounting area on the main surface of a base substrate and in which a first electrode pad on the back of the base substrate is electrically connected to an external terminal on the main surface of the semiconductor pellet.
A semiconductor device with a ball grid array (BGA) structure has been introduced as a semiconductor device having a high level of integration in the Nikkei Electronics, Feb. 28, 1994, pp. 111-117, published by Nikkei McGraw-Hill. The BGA structure of such as semiconductor device, as shown in FIG. 16 (cross section of an essential part), has a semiconductor pellet 2 mounted on a pellet mounting area of the main surface of the base substrate 1 and a plurality of bump electrodes 4 arranged in grid on the back of the base substrate 1 opposite the main surface.
The base substrate 1 may be made from a printed wiring board of two-layer wiring structure. Second electrode pads 1A are arranged in a peripheral area of the main surface of the base substrate 1 (around the pellet mounting area), while first electrode pads 1B are arranged on the back of the base substrate 1 opposite the main surface. The second electrode pads 1A are electrically connected to through-hole conductors 1C via conductors 1A1 arranged on the main surface of the base substrate 1. The first electrode pads 1B are electrically connected to the through-hole conductors 1C via conductors 1B1 arranged on the back of the base substrate 1.
The semiconductor pellet 2 may comprise mainly a semiconductor substrate 2B of single-crystal silicon. On the main surface of the semiconductor substrate 2B (device forming surface) is formed a logic circuit system, a memory circuit system or a combination of these. A plurality of bonding pads 2A are arranged on the main surface of the semiconductor substrate 2B. The bonding pads 2A are formed in the top of the interconnect layers formed on the main surface of the semiconductor substrate 2B.
The bonding pads 2A on the semiconductor pellet 2 are electrically connected to the second electrode pads 1A on the main surface of the base substrate 1 through bonding wires 6. In other words, the bonding pads 2A on the semiconductor pellet 2 are electrically connected to the first electrode pads 1B through the bonding wires 6, second electrode pads 1A, conductors 1A1, through-hole conductors 1C and conductors 1B1.
The semiconductor pellet 2 and the bonding wires 6 are sealed with a resin sealing body 7 formed on the main surface of the base substrate 1. The resin sealing body 7 is formed by transfer molding.
The bump electrodes 4 are electrically and mechanically connected to the surfaces of the first electrode pads 1B on the base substrate 1. The bump electrodes 4 may be formed from an alloy material, such as Pb-Sn.
The semiconductor device of such a BGA structure is mounted on a mounting board, with the bump electrodes 4 electrically and mechanically connected to electrode pads arranged on the mounting surface of the mounting board.
Another example of semiconductor device having a high circuit density is disclosed in U.S. Pat. Ser. No. 5148265, which shows a semiconductor device in which the base substrate is made from a filmlike flexible substrate. In this semiconductor device, the semiconductor pellet is mounted, with its main surface downward, on the pellet mounting area of the main surface of the base substrate made of a flexible substrate, and the bonding pads arranged on the main surface of the semiconductor pellet are electrically connected to the second electrode pads arranged on the back of the base substrate through the bonding wires. The second electrode pads on the base substrate are electrically connected to the first electrode pads on the back of the base substrate through conductors that are also arranged on the back. Bump electrodes are electrically and mechanically connected to the surfaces of the first electrode pads.
The semiconductor device of the above construction is mounted on the mounting surface of a mounting board, with its bump electrodes electrically and mechanically connected to the electrode pads arranged on the mounting surface of the mounting board.